Page 111 - The Handbook for Quality Management a Complete Guide to Operational Excellence

98 I n t e g r a t e d P l a n n i n g S t r a t e g i c P l a n n i n g 99

• The project buffer. A project buffer is established at the end of the
final activity on the Critical Chain, and before the required delivery
date. It’s designed to protect against extreme variability and
uncertainty that may impact the Critical Chain.
• Feeding buffers. Each activity (or sequence of activities) that feeds
the Critical Chain is buffered with some reasonable amount of time
to protect against variability in that particular task, or sequence of
tasks. Feeding buffers protect the Critical Chain from delays
occurring in activities that are not on the Critical Chain. Variability
is all that these buffers protect against. They don’t protect against
multitasking: the tendency of organi zations to assign technical
personnel tasks for different projects or oblig ations simultaneously.
In fact, one of the determinants of success or failure in applying
Critical Chain is the willingness of management to move away
from multitasking.
• Buffer management. A means of control that, at any time in the pro-
ject life, affords project managers the opportunity to determine
how much of various buffers have been used and to take action
as soon as the project appears to be in danger of exceeding its
scheduled time. Task completion delays will cause “penetration”
into buffers, but warning of this happening comes so much earlier
that it’s often possible to prevent schedule overruns sooner, with
considerably less (or less extreme) correc tive action. Monitoring
the buffers, especially the project buffer, results in a higher probability
that the project will complete on time.
• The drum. This concept, similar to that of DBR, applies only to
multiproject situations. The drum concept requires choosing one
of the most heavily loaded resources as the “drum” and
j
staggering multiple pro ects according to the availability of that
resource.
The ultimate effects of Critical Chain project management are
higher deliv ery due date reliability, more frequent earlier delivery, less
“crashing,” and conservation of project costs. Buffer management, in
particular, provides much better focused information on current project
status.

Constraint Management Measurements
One of the unique contributions of the Theory of Constraints to the man-
agement body of knowledge is the measurements used to assess progress
toward the system’s goal. Goldratt recognized some deficiencies inherent
in traditional measurement systems and conceived of a different—more
reliable—way to measure results and evaluate decisions.

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